LOS ANGELES – A Duarte doctor and his assistant, both charged with numerous drug distribution offenses, pleaded not guilty Monday in federal court in Los Angeles.

Dr. Daniel Healy of Arcadia and his assistant, Alvaro Rosales of Chino Hills, were ordered to appear next in court on April 7, the date set for their trial.

Healy was indicted by a federal grand jury last week on 16 drug-related charges; Rosales was indicted on one drug conspiracy charge.

Healy was arrested earlier this month. Rosales was arrested last week, but was released after posting $50,000 bail.

Federal authorities Healy of running cash-only medical practices in Duarte and Rancho Cucamonga that provided massive amounts of prescription drugs to people he knew and trusted, including his sons and their friends.

The narcotics later were often sold on the streets.

Drug databases maintained by the federal government show that Healy dispensed more than 1 million pills of hydrocodone tablets last year – more than any doctor in the nation. Hydrocodone is more commonly known as Vicodin.

Investigators calculated that, based on the hours of operation posted for Healy’s clinic, he dispensed an average of 521 hydrocodone pills an hour.

Healy often asked patients if they preferred a “family size” or “party size” bottle of narcotics, according to a federal criminal complaint.

Rosales also prescribed and distributed pills, even though he was not a doctor, court records allege. He has a degree in medicine from a university in Guadalajara, Mexico, according to authorities, but is not licensed to practice in the United States.

Authorities have also said that several more people are likely to be charged in the case in the near future.